Diaper bags are formed by folding tubular materials made of plastic thin films. When not in use, the folded tubular material is arranged between a mounting disc and an upper cover and is pressed. When in use, a connection device between the upper cover and the mounting disc is opened, and a relatively large storage space is formed in the tubular material. At present, an apparatus for manufacturing axially folded tubular materials performs pressing and folding on an annular cavity disposed in a mould by means of a pressing and folding mechanism, so as to manufacture the axially folded tubular materials. Products manufactured by such an apparatus tend to be uneven and irregular in axial folding, and is inconvenient in use.